Zn2+ dyshomeostasis caused by loss of ATP13A2/PARK9 leads to lysosomal dysfunction and alpha-synuclein accumulation

Mutations in ATP13A2 (PARK9) cause Kufor-Rakeb syndrome (KRS) characterized by juvenile-onset parkinsonism, pyramidal signs and dementia. PARK9 belongs to type 5 P-type ATPase with its putative function as a cation transporter. Loss of PARK9 leads to lysosomal dysfunction and subsequent alpha-synuclein (alpha-Syn) accumulation. However, the mechanistic link between PARK9 and lysosomal dysfunction remains unclear. Here, we found that patient fibroblasts expressing mutant PARK9 or primary neurons with silenced PARK9 exhibited increased sensitivity to extracellular zinc (Zn2+). This effect was rescued with the Zn2+ chelators clioquinol or TPEN. PARK9-deficient cells showed decreased lysosomal sequestration of Zn2+ and increased expression of zinc transporters. Importantly, increased concentrations of Zn2+ (Zn2+ stress) resulted in lysosomal dysfunction that was partially restored by expression of wild-type PARK9. Zn2+ stress also caused increased expression of alpha-Syn and consequently decreased activity of the lysosomal enzyme glucocerebrosidase. Together, these data suggest that PARK9 loss of function leads to dyshomeostasis of intracellular Zn2+ that in turn contributes to lysosomal dysfunction and accumulation of alpha-Syn. It will be of interest to examine whether therapeutic lowering of zinc may prove beneficial for patients with KRS.